The legend's edgecolor property should change the color of the edge of the legend's box. Looking at the sources, changing the edgecolor triggers the updatelegendtext() function. Changing that to updatelegend() won't have an effect as the edgecolor and isn't copied over to the new legend axes that is created before the old one is deleted.

There are similar/related problems with "fontsize" and "interpreter" which trigger the updatelegendtext() as they should, but the legend box does not change its size in response to the change in the extents of this contents.